The research objectives of this project are to contribute to an understanding of the developmental interrelationships between the embryonic brain and its vascular system. An analysis will be made of the effects of mitosis, differentiation, and migration of nervous tissue on the development of cerebrovascular elements. Reciprocal effects of the vascular system on the morphogenesis and histogenesis of the brain will likewise be explored. These influences will be determined during normal development in the chick and mouse, and in abnormal chick embryos whose brains develop defects as a result of experimental manipulation. The interrelationship between cerebrovascularity and neurogenesis will also be examined in mutant embryos of the mouse in which the development of the brain is defective. A variety of techniques will be employed in these studies, including radioautography, biochemistry, scanning and transmission electron microscopy, and tissue culture.